Modulating bypass valve operation?

[bldeng]

We recently had our condenser water / cooling tower control replaced and the contracter installed a control which only cycles the fans on and off to control the water temp. The existing modulating tower bypass valve was not reconnected and the contractor is saying that it should not be needed. Upon our insistance the contractor has agreed to install a seperate control for the modulating valve. My question is, what should the operating range of the valve be? or is it truly not needed? We have a 4 story office building with 12 self contained units with water side economizers, one cooling tower with two single speed fans.
Thanks, Bldeng

 

[DouginMB]

The need for the bypass is dependent on how low the ambient air temperature can drop to. Where is the building?

 

[bldeng]

We are in the Washington D.C. area.
Typical operation is from 4am to 8pm Mon-Fri with maybe two or three unit running on weekends until 6pm.
Thanks,bldeng

 

[lilliput1]

The tower bypass valve should not modulate. It should operate fully open or close. Otherwize tickling water at the tower will freeze. Control so there is adequate deadband in between valve operation.

 

[abcmex]

bldeng,

The cycling of the ventilators may be used to save money when the temperature is cold enough to keep an adequate ECWT at the chiller.

The bypass valve may be used to avoid problems when the water is too cold or to avoid problems in freezing weather, probably DC ;-)